Conventionally, various systems for controlling an engine of a vehicle to automatically control the running speed of the vehicle have been provided. Such control may include constant speed running control, accelerated or decelerated running control or the like. Probably, for example, constant speed running control is normally executed during running at a set speed, but when the set speed is changed or when it is intended to make accelerated or decelerated running, accelerated or decelerated running control is executed.
By the way, control of an engine for such automatic control of a vehicle involves adjustment of the opening of a throttle valve of the engine so as to cause the engine to output a sufficient torque for the vehicle to run while maintaining a predetermined speed or while maintaining a predetermined acceleration.
For the adjustment of the opening of a throttle valve, it is necessary to discriminate a torque (actual torque) which is actually being outputted by an engine. Various calculating means are provided for the calculation of an actual torque. For example, an actual torque may be determined, for example, from characteristics of the engine such as an amount of intake air of the engine or a speed of rotation of the engine.
However, a calculated value of an actual torque must be a value of a torque which is actually produced at a stage of each control cycle and includes a minimum time delay. Otherwise, the responsability may possibly be deteriorated in control executed in accordance with the actual torque, and running control of the vehicle may not be executed in a desired manner.
The present invention has been made in view of such a subject as described above, and it is an object of the present invention to provide an engine controlling system for a vehicle which can calculate an actual torque having a minimum time delay to improve the responsibility in control of an engine which is executed in accordance with such actual torque.